Speaker
Mickey Chiu
(Brookhaven National Lab)
Description
Determining the contribution of gluon spin to the proton's total spin is one of the crucial ingredients in resolving the proton spin puzzle. Hints from recent measurements of double longitudinal asymmetries ($A_{LL}$) from the Relativistic Heavy Ion Collider (RHIC) suggest $\Delta g$ is non-zero at moderate values of Bjorken $x \sim 10^{-2}$. In the PHENIX experiment at RHIC, we have a forward $PbWO_{4}$ electromagnetic calorimeter, the MPC, with acceptance in the region $3.1<|\eta|<3.9$, and sensitivity to $\Delta g$ down to Bjorken $x \sim 10^{-3}$. It is important to probe down to low-x since much of the gluon spin contribution to the proton may come from lower x. We will present the status and challenges of the PHENIX measurement of the double longitudinal spin asymmetries, $A_{LL}$, from longitudinally polarized proton collisions at center of mass energies of 200, 500, and 510 GeV taken over the 2009-2012 period.
Author
Mickey Chiu
(Brookhaven National Lab)
